Bowstring mounted peep sights are generally of two types. A first type, illustrated for example in U.S. Pat. No. 4,454,857, U.S. Pat. Nos. 4,860,458 and 4,934,332, comprises an archery bow peep sight in the form of a disk or a wheel having an annular or circumferential opening therein and/or a central aperture. The peep sight is designed to be mounted horizontally such that the axis of the peep is the same as the line of the bowstring. The sight may be mounted either with a multi-stranded bowstring passing through the central aperture or with the strands of a divided multifilament bowstring received in vertical slots in the periphery of the sight body. When the bow is drawn the disk or wheel is tilted revealing to the archer one or more sighting paths through the annular or circumferential openings. Unfortunately, very little of the available light passes through such a peep and the archer's field of view is severely limited.
Another type of peep sight, illustrated for example in U.S. Pat. No. 7,040,027, takes the form of a mounting member having generally vertically disposed side channels serving as guides for receiving the strands of a divided multifilament bowstring. The peep is formed within or supported by the mounting member with its axis generally perpendicular to the riser, i.e., parallel to the axis of an arrow nocked in the bowstring and resting on an arrow rest supported by the riser. In one form of this type of peep sight, a sighting member including a peep aperture of desired shape is slidably and interchangeably received in a channel of the mounting member. However, in this type of peep sight, wherein the peep aperture is surrounded substantially 360° by solid material, a similar problem is encountered as with other peep sights in that insufficient available light is able to pass through the aperture to permit clear and easy sighting. In addition, the field of view through such peep apertures is extremely limited. As a result, game may be missed because of inadequate lighting or simply because the archer cannot see clearly through the peep. In a modification of this type of peep sight, illustrated in U.S. Pat. No. 6,024,079, the mounting member is supported between the filaments of the bowstring and the sighting member is supported by the mounting member, but the peep opening in the sighting member is not positioned between the filaments of the multifilament bowstring. Rather, the sighting member is offset from the mounting body and the bowstring by an angle of about 35° before the bow is drawn and tilts or rotates when the bow is fully drawn to a position wherein the line of sight through the peep is aligned with the front sight and parallel to an arrow correctly mounted in the bow. The peep itself is formed as an opening within the sighting member and may be any shape, such as square or oval, but preferably is semi-circular with a very small gap formed in the wall of the sighting member communicating with the opening to allow additional light to enter the opening. However, the offset arrangement of the sighting member, the inability to sight until the bow is fully drawn and the use of only a very small gap in the peep opening contributes to a peep sight which still transmits insufficient light for good sighting and severely restricts the field of view.
Despite the problems with prior art bowstring mounted peep sights, an archer is seldom better off without a peep sight. Without a peep sight, the archer's vision moves in toward the riser, thereby greatly reducing the field of view. In addition, the archer frequently encounters the halo effect which occurs when trying to look to just one side of the bowstring, with the result that clear vision is impeded.
Accordingly, there is a need for a rear sight which can be mounted as a string splitter sight between the strands of a multifilament bowstring yet which allows almost 100% of available light transmission through the sight and which substantially increases an archer's field of view. In addition, there is a need for a rear sight which allows maximum view of the target during a shot, which can be used with or without a kisser button, which eliminates bulky sight systems and which only nominally reduces arrow speed as compared with a bare bowstring.